Image inspection apparatus and image forming apparatus using reading result of incident light reflected from target both via and not via light guide member

ABSTRACT

An image inspection apparatus includes: an illumination part that emits light on an inspection target; a reading part that is arranged with, in one or more dimensions, elements that detect light reflected by the inspection target, the reading part reading an entire width of the inspection target; and a hardware processor that inspects a characteristic of the inspection target, wherein a light guide member is provided at a position where light regularly reflected by the inspection target passes, the light guide member is arranged to allow an optical path of light incident on the reading part via the light guide member to be parallel to an optical path of light incident on the reading part without via the light guide member, and the hardware processor inspects a gloss distribution of the inspection target, and inspects a density distribution of the inspection target.

The entire disclosure of Japanese patent Application No. 2019-107614,filed on Jun. 10, 2019, is incorporated herein by reference in itsentirety.

BACKGROUND Technological Field

The present invention relates to an image inspection apparatus and animage forming apparatus, and more particularly, to an image inspectionapparatus for inspecting a characteristic of a sheet, and an imageforming apparatus including the image inspection apparatus.

Description of the Related Art

In an image forming apparatus such as a multi-functional peripheral(MFP) that prints image information on a sheet by using anelectrophotographic process, image quality greatly varies withenvironmental changes such as temperature and humidity, temporal changesof materials and parts, and the like, even when trying to maintaincertain image quality. Therefore, image information is inspected by asensor or the like that measures a density, and an inspection result isfed back to an image process. In recent years, there has been widespreaduse of image forming apparatuses that can read a sheet printed withimage information by an image inspection apparatus and feed back theread density, color, and position information to an image process, inorder to further improve the quality of images.

Regarding such an image inspection apparatus, for example, JP2012-247280 A discloses an image inspection apparatus for inspecting adensity distribution and a gloss distribution of an image on an objectto be inspected that are acquired based on a light amount of diffusereflection light and a light amount of regular reflection light receivedby an optical reading part. The image inspection apparatus includes: adensity distribution inspection illumination part that emits densitydistribution inspection illumination light on an object to be inspectedon which an image is formed; a gloss distribution inspectionillumination part that emits gloss distribution inspection illuminationlight on the object to be inspected; and the optical reading part thatreceives diffuse reflection light and regular reflection light reflectedfrom the object to be inspected. The density distribution inspectionillumination part emits the density distribution inspection illuminationlight that is visible light, the gloss distribution illumination partemits the gloss distribution inspection illumination light that isinvisible light, and the optical reading part includes: a first opticalreading part that simultaneously lights the density distributioninspection illumination part and the gloss distribution illuminationpart and exclusively receives the diffuse reflection light of visiblelight diffused and reflected by an image forming material after beingtransmitted inside an image on the object to be inspected, to output adensity distribution based on an amount of the diffuse reflection light;and a second optical reading part that exclusively receives the regularreflection light of invisible light that is regularly reflected from asurface of an image on the object to be inspected, to output a glossdistribution based on an amount of regular reflection light.

Even with an image forming apparatus that can read a sheet printed withimage information with an image inspection apparatus and compare theread image information with original image information to inspect aprinting state, simply reading a density may not enable propermaintenance of image quality. For example, when printing a backgroundand a target in a same color system, the target appears to be floatingeven if the density is controlled, because there is a difference ingloss between the background and the target even in similar colors.Further, even in printing that gives gloss by decorating, it is notpossible to properly express a difference between glossy silver andmatte silver even by controlling the density.

To solve this problem, as disclosed in JP 2012-247280 A, a method ofcontrolling the gloss by detecting an amount of regular reflection lighthas been proposed. However, it is necessary to read regular reflectionlight reflected in the entire area in order to inspect the entire areaof a sheet to be printed by the image forming apparatus, and it isnecessary to dispose a sensor at a distant in order to read the regularreflection light, causing a problem that the image inspection apparatusbecomes too large to be mounted to the image forming apparatus.

SUMMARY

The present invention has been made in view of the above problems, and amain object of the present invention is to provide an image inspectionapparatus that can be mounted to an image forming apparatus, and canmeasure a gloss distribution over the entire surface of a sheet, and animage forming apparatus.

To achieve the abovementioned object, according to an aspect of thepresent invention, an image inspection apparatus reflecting one aspectof the present invention comprises: an illumination part that emitslight on an inspection target; a reading part that is arranged with, inone or more dimensions, elements that detect light reflected by theinspection target, the reading part reading an entire width of theinspection target; and a hardware processor that inspects acharacteristic of the inspection target based on a reading result of thereading part, wherein a light guide member is provided at a positionwhere light regularly reflected by the inspection target passes, thelight guide member is arranged to allow an optical path of lightincident on the reading part via the light guide member to be parallelto an optical path of light incident on the reading part without via thelight guide member, and the hardware processor inspects a glossdistribution of the inspection target based on a reading result of lightincident on the reading part via the light guide member, and inspects adensity distribution of the inspection target based on a reading resultof light incident on the reading part without via the light guidemember.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features provided by one or more embodiments of theinvention will become more fully understood from the detaileddescription given hereinbelow and the appended drawings which are givenby way of illustration only, and thus are not intended as a definitionof the limits of the present invention:

FIG. 1 is a diagram illustrating an example of a configuration of aprinting system according to one embodiment of the present invention;

FIG. 2 is a diagram illustrating another example of the configuration ofthe printing system according to one embodiment of the presentinvention;

FIG. 3 is a diagram illustrating another example of the configuration ofthe printing system according to one embodiment of the presentinvention;

FIGS. 4A and 4B are block diagrams illustrating a configuration of animage forming apparatus according to one embodiment of the presentinvention;

FIG. 5 is a schematic view illustrating an example of a structure of theimage forming apparatus according to one embodiment of the presentinvention;

FIG. 6 is a flowchart illustrating an operation of the image formingapparatus according to one embodiment of the present invention;

FIG. 7 is a schematic view illustrating an example of a structure of animage inspection part in the image forming apparatus according to oneembodiment of the present invention (when a gloss distribution alone isread);

FIG. 8 is a schematic view illustrating another example of the structureof the image inspection part in the image forming apparatus according toone embodiment of the present invention (when a gloss distribution and adensity distribution are read by one reading part);

FIG. 9 is a schematic view illustrating another example of the structureof the image inspection part in the image forming apparatus according toone embodiment of the present invention (when a gloss distribution and adensity distribution are read by different reading parts);

FIG. 10 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when regularreflection light and diffused light are reflected by a reflectingmember);

FIG. 11 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when alight-transmitting member is arranged between an inspection target and alight guide member);

FIG. 12 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when thelight-transmitting member is arranged to be inclined);

FIGS. 13A and 13B are schematic views illustrating another example ofthe structure of the image inspection part in the image formingapparatus according to one embodiment of the present invention (when aposition maintaining member is installed on the light-transmittingmember);

FIG. 14 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when thelight-transmitting member installed with the position maintaining memberis arranged to be inclined);

FIG. 15 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when the imageinspection parts provided with the light-transmitting member arearranged on both sides of the inspection target); and

FIG. 16 is a schematic view illustrating another example of thestructure of the image inspection part in the image forming apparatusaccording to one embodiment of the present invention (when the imageinspection parts provided with the light-transmitting member and theposition maintaining member are arranged on both sides of the inspectiontarget.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, one or more embodiments of the present invention will bedescribed with reference to the drawings. However, the scope of theinvention is not limited to the disclosed embodiments.

As described in Description of the Related art, in an image formingapparatus that uses an electrophotographic process to print imageinformation on a sheet, image quality greatly varies due toenvironmental changes such as temperature and humidity and temporalchanges of materials and components. For this reason, image informationis inspected by a sensor or the like that measures a density, and aninspection result is fed back to an image process, and image formingapparatuses having an image inspection apparatus have become widespreadin recent years.

However, even in an image forming apparatus provided with such an imageinspection apparatus, it is not possible to properly maintain imagequality by simply reading the density. For example, due to a differencein gloss between a background and a target even for similar colors, thetarget appears to be floating even when the density is controlled, andit is not possible to appropriately express a difference between glossysilver and matte silver even when controlling the density. To solve thisproblem, a method of controlling the gloss by detecting an amount ofregular reflection light has been proposed. However, it is necessary toread regular reflection light reflected in the entire area in order toinspect the entire area of a sheet, and it is necessary to dispose asensor at a distant in order to read the regular reflection light,causing a problem that the image inspection apparatus becomes too largeto be mounted to the image forming apparatus.

Therefore, in an embodiment of the present invention, regular reflectionlight from a sheet is returned in a direction other than a main scanningdirection of the sheet (desirably, in a normal direction of the sheet ora sub scanning direction of the sheet) by using a light guide membersuch as a mirror. Specifically, in an image inspection apparatusincluding: an illumination part that emits light on an inspectiontarget; a reading part that is arranged with, in one or more dimensions,elements that detect light reflected by the inspection target, and readsan entire width of the inspection target; and a control part thatinspects a characteristic of the inspection target based on a readingresult of the reading part, a light guide member is provided at aposition where light regularly reflected by the inspection targetpasses, the light guide member is arranged to allow an optical path oflight incident on the reading part via the light guide member to beparallel to an optical path of light incident on the reading partwithout via the light guide member, and the control part inspects agloss distribution of the inspection target based on a reading result oflight incident on the reading part via the light guide member, andinspects a density distribution of the inspection target based on areading result of light incident on the reading part without via thelight guide member.

In this way, by returning the regular reflection light from the sheet ina direction other than the main scanning direction of the sheet by usingthe light guide member such as a mirror, the image inspection apparatuscan be downsized and mounted to the image forming apparatus. Then, usingthe image forming apparatus mounted with the image inspection apparatusenables appropriate feedback of an image inspection result to an imageprocess, to maintain favorable image quality.

EXAMPLE

In order to explain the one embodiment of the present inventiondescribed above in more detail, an image inspection apparatus and animage forming apparatus according to an embodiment of the presentinvention will be described with reference to FIGS. 1 to 16. FIGS. 1 to3 are schematic diagrams illustrating a configuration of a printingsystem according to the present embodiment, FIGS. 4A and 4B are blockdiagrams illustrating a configuration of the image forming apparatusaccording to the present embodiment, and FIG. 5 is a schematic viewillustrating an example of a structure of the image forming apparatusaccording to the present embodiment. FIG. 6 is a flowchart illustratingan operation of the image forming apparatus according to the presentembodiment, and FIGS. 7 to 16 are schematic views illustrating astructure of an image inspection part in the image forming apparatusaccording to the present embodiment.

As illustrated in FIG. 1, a printing system 10 of the present embodimentincludes a controller 11 that performs raster image processing (RIP)processing on a print job inputted from a computer device (notillustrated) or the like, an image forming apparatus 12 that forms animage on a sheet based on image data after the RIP processing, an imageinspection apparatus 13 that inspects the sheet formed with the image,and the like. These are connected to be able to perform datacommunication via a communication network 14 such as a local areanetwork (LAN) defined by a standard such as Ethernet (registeredtrademark), token ring, and fiber-distributed data (FDDI), or a widearea network (WAN).

Note that, in FIG. 1, the printing system 10 is formed by the controller11, the image forming apparatus 12, and the image inspection apparatus13, but the printing system 10 can also be formed by the controller 11and the image forming apparatus 12 as illustrated in FIG. 2, when theimage inspection apparatus 13 is mounted to the image forming apparatus12. Further, when providing the image forming apparatus 12 with afunction as the controller 11, as illustrated in FIG. 3, the printingsystem 10 may be formed by the image forming apparatus 12 alone.Hereinafter, for facilitating explanation, the description will be madeassuming the configuration of FIG. 3.

As illustrated in FIG. 4A, the image forming apparatus 12 in theconfiguration of FIG. 3 includes a control part 20, a storage part 21,an image processing part 22, a print processing part (engine) 23, animage inspection part 24, a display operation part 25, and the like.

The control part 20 includes a central processing unit (CPU) 20 a andmemories such as a read only memory (ROM) 20 b and a random accessmemory (RAM) 20 c, which are connected via a bus. The CPU 20 a performsoverall control of the image forming apparatus 12 by reading out acontrol program from the ROM 20 b and the storage part 21, developingthe control program into the RAM 20 c, and executing the controlprogram.

The storage part 21 is formed by a hard disk drive (HDD), a solid statedrive (SSD), and the like, and stores a program for the CPU 20 a tocontrol each part, a print job received from an external computer deviceand the like, image data generated from the print job, image information(a gloss distribution and a density distribution) read by the imageinspection part 24, image forming conditions, and the like.

The image processing part 22 translates a print job described in pagedescription language (PDL) such as printer control language (PCL) orpost script (PS) to generate intermediate data, uses a color conversiontable to perform color conversion on the intermediate data, and performsrendering to generate image data of a print image (this series ofprocessing is called RIP processing). Further, the image processing part22 performs image processing such as color adjustment, densityadjustment, size adjustment, and screening (halftone dot processing) onthe print image after the RIP processing.

The print processing part 23 is an engine that executes print processingbased on a print image. Specifically, the print processing part 23includes an exposure part that emits a laser beam to expose based on aprint image, a photoreceptor drum, a developing device, a chargingdevice, a photoreceptor cleaning part, and a primary transfer roller,and formed by: an image forming part that forms a toner image of eachcolor of yellow (Y), magenta (M), cyan (C), and black (K); anintermediate transfer belt that is rotated by a roller and functions asan intermediate transfer body that conveys the toner image formed by theimage forming part to a sheet; a secondary transfer roller thattransfers the toner image formed on the intermediate transfer belt to asheet; a fixing part that fixes the toner image transferred to thesheet; a sheet feeding part such as a sheet feeding tray; a sheetdischarging part such as a sheet discharging tray; and a conveyance partsuch as a sheet feeding roller, a resist roller, a loop roller, areversing roller, and a sheet discharging roller, for conveyance of asheet.

Further, the print processing part 23 can select between a single-sidedprinting mode for printing on one side alone of the sheet and adouble-sided printing mode for printing on both sides of the sheet. In acase of the double-sided printing mode, as shown by a solid line arrowin FIG. 5, a sheet is conveyed from the sheet feeding part, a printimage is formed on a front side of the sheet by the print processingpart 23 (image forming part), the print image is fixed by the printprocessing part 23 (fixing part), and the image inspection part 24 readsimage information on the front side of the sheet. Thereafter, the sheetis conveyed by the resist roller and the loop roller, turned over by thereversing roller, and conveyed again to the image forming part. Then, asshown by a dashed arrow in FIG. 5, a print image is formed on a backside of the sheet by the image forming part, the print image is fixed bythe fixing part, and the image inspection part 24 reads imageinformation of the back side of the sheet. Alternatively, afterformation of print images on both sides of the sheet, image informationon both sides of the sheet is read by using the image inspection parts24 arranged on both sides of the sheet.

The image inspection part 24 reads image information of an inspectiontarget (sheet). The image inspection part 24 includes an illuminationpart, a light guide member, a reading part, and, if necessary, areflecting member, a light-transmitting member, a position maintainingmember, and the like. The image inspection part 24 is provided to, forexample, a sheet conveyance path between the fixing part of the printprocessing part 23 and the sheet discharging tray. Note that thedetailed configuration of the image inspection part 24 will be describedlater.

The display operation part 25 is a touch panel or the like in which atouch sensor formed by a grid-shaped transparent electrode is formed ona display part such as a liquid crystal display (LCD) or an organicelectro luminescence (EL) display, and displays various screens relatedto image formation and enables various operations related to imageformation on the screen.

As illustrated in FIG. 4B, the control part 20 of the image formingapparatus 12 also functions as a gloss distribution acquisition part 26,a density distribution acquisition part 27, a feedback part 28, and thelike, and inspects a characteristic of the inspection target.

The gloss distribution acquisition part 26 acquires a gloss distributionof the inspection target, based on a reading result of regularreflection light reflected by the entire width of the inspection targetby the reading part of the image inspection part 24.

The density distribution acquisition part 27 acquires a densitydistribution of the inspection target, based on a reading result ofdiffused light reflected by the entire width of the inspection target bythe reading part of the image inspection part 24.

The feedback part 28 adjusts image forming conditions of the imageforming part based on the gloss distribution acquired by the glossdistribution acquisition part 26 and the density distribution acquiredby the density distribution acquisition part 27. For example, if acharging voltage (minus voltage) of the photoreceptor drum deviates froma desired value, the density distribution varies. Therefore, the imageforming conditions are adjusted such that the charging voltage islowered (increased) in a portion where the density is low (high).Further, if a fixing temperature is high, a toner is crushed well andthe gloss increases. Therefore, the image forming conditions areadjusted such that the fixing temperature is increased (decreased) in aportion where the gloss is low (high).

The gloss distribution acquisition part 26, the density distributionacquisition part 27, and the feedback part 28 may be formed as hardware.Alternatively, the control part 20 may be adapted as an image inspectionprogram for functioning as the gloss distribution acquisition part 26,the density distribution acquisition part 27, and the feedback part 28,and the CPU 20 a may execute the image inspection program.

Note that FIGS. 4A and 4B are examples of the image forming apparatus 12of the present embodiment, and the configuration thereof can be changedas appropriate. For example, in FIGS. 4A and 4B, the image formingapparatus 12 having the function of the image inspection apparatus 13has been described. However, when functioning as the image inspectionapparatus 13 alone, it is possible to omit the image processing part 22,the print processing part 23, and the like from the configuration inFIGS. 4A and 4B, and the control part of the image inspection apparatus13 may function as the gloss distribution acquisition part 26, thedensity distribution acquisition part 27, and the feedback part 28 (theCPU of the control part executes the image inspection program).

Hereinafter, an image inspection method using the image formingapparatus 12 having the configuration illustrated in FIGS. 4A and 4Bwill be described. The CPU 20 a executes processing of each stepillustrated in the flowchart of FIG. 6, by developing the imageinspection program stored in the ROM 20 b or the storage part 21 intothe RAM 20 c and executing the image inspection program.

First, the image inspection part 24 reads regular reflection light thatis regularly reflected on a sheet, and diffused light that is diffusedon the sheet (S101). In a case of forming an image on both sides of thesheet, a back side of the sheet can be inspected by reversing the sheetand forming an image again on the back side of the sheet afterinspection of a front side of the sheet, or both sides of the sheet canbe inspected using the image inspection parts 24 arranged on both sidesof the sheet, after formation of an image on both sides of the sheet.

Next, the control part 20 (the gloss distribution acquisition part 26)acquires a gloss distribution of the inspection target, based on areading result of regular reflection light reflected by the entire widthof the inspection target by the reading part of the image inspectionpart 24 (S102).

Next, the control part 20 (the density distribution acquisition part 27)acquires a density distribution of the inspection target, based on areading result of diffused light reflected by the entire width of theinspection target by the reading part of the image inspection part 24(S103).

Then, the control part 20 (the feedback part 28) adjusts image formingconditions of the image forming part based on the gloss distributionacquired by the gloss distribution acquisition part 26 and the densitydistribution acquired by the density distribution acquisition part 27(S104).

Hereinafter, a specific structure of the image inspection part 24 of thepresent embodiment will be described with reference to schematic viewsof FIGS. 7 to 16. In FIGS. 7 to 16, a structure (a conveyance roller orthe like) for conveyance of a sheet as the inspection target 30 isomitted. Further, the inspection target 30 is conveyed from left toright in the figure, and a depth direction in the figure is a mainscanning direction (width direction), and a left-right direction in thefigure is a sub scanning direction (conveyance direction).

FIG. 7 shows a basic structure of the image inspection part 24 of thepresent embodiment. The image inspection part 24 includes at least: anillumination part 31 that emits light on the inspection target 30 suchas a sheet; a light guide member 32 that guides light regularlyreflected on the inspection target 30 in a direction other than the mainscanning direction (width direction) of the inspection target 30 (in anormal direction or the sub scanning direction); and a reading part 33that is arranged with, in one or more dimensions, elements that detectlight reflected by the inspection target 30, and reads an entire widthof the inspection target 30.

The illumination part 31 is formed by a light emitting diode (LED), alaser oscillator, or the like, and emits light such as visible light orinfrared light at a predetermined angle over the entire width of theinspection target 30. Note that, in the present embodiment, in order todetect at least regular reflection light, the light emitted from theillumination part 31 desirably has a certain degree of directivity.

The light guide member 32 is a mirror, an optical fiber, or the like,and is disposed at a position where light regularly reflected by theinspection target 30 passes. By returning the regular reflection lightin a direction other than the main scanning direction with the lightguide member 32, the image inspection part 24 can be downsized.

The reading part 33 is, for example, a linear sensor in which a sensorsuch as a charge coupled device (CCD) or a complementary metal oxidesemiconductor (CMOS) is arranged in one dimension (in the main scanningdirection, that is, in the depth direction in the drawing), or an arraysensor in which the sensor is arranged in two dimensions (the mainscanning direction and the sub scanning direction). The reading part 33outputs a signal corresponding to an amount of light reflected by thesheet. In FIG. 7, the gloss distribution of the inspection target 30 canbe acquired by reading the regular reflection light that is incident viathe light guide member 32.

In FIG. 7, the light regularly reflected by the inspection target 30 isexclusively read. However, as illustrated in FIG. 8, in addition toacquiring the gloss distribution of the inspection target 30 by readingthe light regularly reflected by the inspection target 30, the densitydistribution of the inspection target may be acquired by reading lightdiffused by the inspection target 30. In this case, the light guidemember 32 is arranged such that an optical path of the regularreflection light incident on the reading part 33 via the light guidemember 32 is parallel to an optical path of the diffused light incidenton the reading part 33 without via the light guide member 32, and theregular reflection light and the diffused light can be read by movingthe reading part 33 or converging the light by an optical system such asa lens.

Further, in the present embodiment, the regular reflection light and thediffused light of the light emitted from one illumination part 31 areread. However, a plurality of illumination parts 31 may be provided, andthe regular reflection light of light emitted from a first illuminationpart may be read while the diffused light of light emitted from a secondillumination part may be read. In that case, wavelengths of lightemitted from the plurality of illumination parts 31 may be the same, orthe wavelengths may be different such that the first illumination partis for an infrared region while the second illumination part is for avisible region.

In this way, by using one reading part 33 to read the light regularlyreflected by the inspection target 30 and the light diffused by theinspection target 30, it is possible to acquire the gloss distributionand the density distribution of the inspection target 30, andappropriately adjust image forming conditions.

In FIGS. 7 and 8, one reading part 33 is used to read the regularreflection light, or the regular reflection light and diffused light.However, as illustrated in FIG. 9, the reading part 33 may be formed bya first reading part 33 a and a second reading part 33 b, to readregular reflection light with the first reading part 33 a to acquire agloss distribution and read diffused light with the second reading part33 b to acquire a density distribution.

In this way, by separately providing the first reading part 33 a toacquire the gloss distribution and the second reading part 33 b toacquire the density distribution, it is not required to provide amechanism to move the reading part 33, and the gloss distribution andthe density distribution can be simultaneously acquired. In addition,since a sensor suitable for detecting regular reflection light ordiffused light (for example, a sensor having a different detectionwavelength or detection sensitivity) can be used, image formingconditions can be appropriately adjusted.

In FIGS. 7 to 9, the light is reflected in the normal direction of theinspection target 30 by using the light guide member 32. However, thereis a case where there is not enough space, in the normal direction ofthe inspection target 30, for arranging the reading parts 33 in whichelements are arranged in the main scanning direction (width direction)of the sheet, or a case where external light intrudes from the normaldirection of the inspection target 30 due to the structure of theapparatus. In this case, in the present embodiment, since the regularreflection light incident on the reading part 33 via the light guidemember 32 is parallel to the diffused light incident on the reading part33 without via the light guide member 32, as illustrated in FIG. 10, theregular reflection light and the diffused light can be reflected(reflected at least once in the sub scanning direction of the inspectiontarget 30) by the reflecting member 34 such as a mirror. Here, theregular reflection light and the diffused light are reflected threetimes by the three reflecting members 34, but the number, a size, and areflection angle of the reflecting member 34 are not limited to theconfiguration illustrated in the figure, and the light may be collectedby forming the reflecting member 34 with a concave mirror or the like.

Thus reflecting both the regular reflection light and the diffused lightenables changing of the installation location of the reading part 33,and allows the size of the entire image inspection part 24 to becompact. Note that, in FIG. 10, the reflecting member 34 is arranged forthe configuration including the first reading part 33 a and the secondreading part 33 b, but the reflecting member 34 may also be arranged forthe configuration including one reading part 33.

In FIGS. 7 to 10, the image inspection part 24 is formed by theillumination part 31, the light guide member 32, the reading part 33(the first reading part 33 a and the second reading part 33 b), and asnecessary, the reflecting member 34. However, when a sheet is conveyed,contaminants such as toner and fibers may adhere to the light guidemember 32, the reading part 33, and the like, to deteriorate accuracy ofreading of the regular reflection light and the diffused light. In sucha case, as illustrated in FIG. 11, a light-transmitting member 35 madeof glass or the like is arranged between the inspection target 30, andthe illumination part 31 and the light guide member 32 (for example, ata distance of about 1 mm from the inspection target 30). It sufficesthat the light-transmitting member 35 can transmit the light emittedfrom the illumination part 31, and a material, a size, a thickness, andthe like can be appropriately set. In addition, any method of installingthe light-transmitting member 35 may be adopted, and for example, thelight-transmitting member 35 can be fixed to a guide plate (notillustrated) that forms a sheet conveyance path.

Thus arranging the light-transmitting member 35 enables the imageinspection part 24 to be dustproof. Note that, in FIG. 11, thelight-transmitting member 35 is disposed for the configuration of FIG.10, but the light-transmitting member 35 may be disposed for theconfiguration of FIGS. 7 to 9.

In FIG. 11, the light-transmitting member 35 is installed in parallelwith the inspection target 30. However, when the light-transmittingmember 35 is disposed in parallel with the inspection target 30, lightincident on the light-transmitting member 35 from the illumination part31 may be totally reflected on a surface of the light-transmittingmember 35 and no longer be incident on the inspection target 30, orlight incident on the light-transmitting member 35 (directly incidentfrom the illumination part 31 or reflected on the inspection target 30to be incident) may be multiply reflected inside the light-transmittingmember 35. In such a case, as illustrated in FIG. 12, thelight-transmitting member 35 can be arranged to be inclined so as not tobe parallel to the inspection target 30. Note that an angle of theinclination of the light-transmitting member 35 can be appropriately setin accordance with a positional relationship (regular reflection angle)between the inspection target 30, the illumination part 31, and thelight guide member 32, and can be set to, for example, about 10°.

Thus inclining the light-transmitting member 35 can suppress an effectof total reflection by the light-transmitting member 35, and allows thelight-transmitting member 35 for dust prevention to be arranged even inthe image inspection part 24 that reads regular reflection light.

The inspection target 30 is conveyed by the conveyance roller providedin the sheet conveyance path. However, when a position of the inspectiontarget 30 fluctuates on the sheet conveyance path, such as when theinspection target 30 sinks between the conveyance rollers, an incidentangle of the light incident on the inspection target 30 from theillumination part 31 changes, which may disable accurate detection ofthe regular reflection light, or may cause the inspection target 30 tocome into contact with the light-transmitting member 35 and stain thelight-transmitting member 35. In such a case, as illustrated in FIG.13A, a position maintaining member 36 that maintains a position of theinspection target 30 can be arranged near the conveyance path of theinspection target 30. It suffices that the position maintaining member36 can maintain the position of the inspection target 30, and may bemade by, for example, polyethyleneterephthalate (PET), and can beinstalled on the inspection target 30 side of the light-transmittingmember 35 as illustrated in FIG. 13B.

Thus providing the position maintaining member 36 enables suppression offluctuation in the position of the inspection target 30 on the sheetconveyance path, and prevention of stain on the light-transmittingmember 35. In FIGS. 13A and 13B, the position maintaining member 36 isarranged in the configuration of FIG. 11, but the position maintainingmember 36 may be arranged in the configurations of FIGS. 7 to 10.

In FIGS. 13A and 13B, the position maintaining member 36 is installed onthe light-transmitting member 35 arranged in parallel with theinspection target 30, but the position maintaining member 36 may beinstalled to the light-transmitting member 35 arranged to be inclinedwith respect to the inspection target 30, as illustrated in FIG. 14. Inthis case, the light-transmitting member 35 may be inclined in anydirection with respect to the inspection target 30. However, theposition maintaining member 36 is to be disposed at a portion where adistance between the inspection target 30 and the light-transmittingmember 35 is small, and the position of the inspection target 30 can bereliably maintained when the position maintaining member 36 is arrangedon an upstream side of the inspection target 30. Therefore, thelight-transmitting member 35 is desirably inclined so as to narrow thedistance on the upstream side of the inspection target 30.

Thus installing the position maintaining member 36 on thelight-transmitting member 35 arranged to be inclined enables maintenanceof the position of the inspection target 30, and suppression of aneffect of total reflection by the light-transmitting member 35.

In FIGS. 7 to 14, the image inspection part 24 is arranged on one side(a lower side in the figure) of the inspection target 30. However, whenthe print processing part 23 can form images on both sides of the sheet,and inspection is performed on both sides of the sheet, as illustratedin FIG. 15, a first image inspection part 24 a may be arranged on oneside of the inspection target 30, and a second image inspection part 24b may arranged on the other side.

Thus arranging the image inspection parts 24 on both sides of theinspection target 30 enables simultaneous inspection of both sides ofthe inspection target 30, and reduction of an inspection time. Althoughthe image inspection parts 24 having the configuration of FIG. 12 arearranged on both sides of the inspection target 30 in FIG. 15, the imageinspection parts 24 having the configurations of FIGS. 7 to 11 may bearranged on both sides of the inspection target 30.

Further, in FIG. 15, the image inspection part 24 including theillumination part 31, the light guide member 32, the reading part 33,the reflecting member 34, and the light-transmitting member 35 isarranged on both sides of the inspection target 30. However, asillustrated in FIG. 16, the image inspection part 24 including theposition maintaining member 36 may be arranged on both sides of theinspection target 30. In this configuration, the inspection target 30 isheld by the position maintaining member 36 arranged on both sides.Therefore, the position of the inspection target 30 can be held morereliably, and accuracy of reading regular reflection light can beimproved.

As described above, by returning the light regularly reflected by theinspection target 30 in a direction other than the main scanningdirection (in the normal direction, the sub scanning direction, or thelike) of the inspection target 30 by using the light guide member 32such as a mirror, the image inspection part 24 can be downsized to bemounted to the image forming apparatus 12. Then, using the image formingapparatus 12 mounted with the image inspection part 24 enablesappropriate feedback of an image inspection result to the image process,to maintain favorable image quality.

Note that the present invention is not limited to the above embodiment,and the configuration and control of the image forming apparatus 12 canbe appropriately changed without departing from the spirit of thepresent invention.

For example, in the above embodiment, the image forming apparatus 12mounted with the image inspection part 24 has been described, but thepresent invention is similarly applied to a case where an imageinspection apparatus 13 different from the image forming apparatus 12 isused.

The present invention is applicable to an image inspection apparatus forinspecting a characteristic of a sheet, and an image forming apparatusmounted with the image inspection apparatus.

Although embodiments of the present invention have been described andillustrated in detail, the disclosed embodiments are made for purposesof illustration and example only and not limitation. The scope of thepresent invention should be interpreted by terms of the appended claims.

What is claimed is:
 1. An image inspection apparatus comprising: anillumination part that emits light on an inspection target; a readingpart that is arranged with, in one or more dimensions, elements thatdetect light reflected by the inspection target, the reading partreading an entire width of the inspection target; and a hardwareprocessor that inspects a characteristic of the inspection target basedon a reading result of the reading part, wherein a light guide member isprovided at a position where light regularly reflected by the inspectiontarget passes, the light guide member is arranged to allow an opticalpath of light incident on the reading part via the light guide member tobe parallel to an optical path of light incident on the reading partwithout via the light guide member, and the hardware processor inspectsa gloss distribution of the inspection target based on a reading resultof light incident on the reading part via the light guide member, andinspects a density distribution of the inspection target based on areading result of light incident on the reading part without via thelight guide member.
 2. The image inspection apparatus according to claim1, wherein the light guide member is a mirror.
 3. The image inspectionapparatus according to claim 1, wherein the reading part includes afirst reading part that reads light incident via the light guide member,and a second reading part that reads light incident without via thelight guide member.
 4. The image inspection apparatus according to claim1, further comprising: a reflecting member that reflects light incidenton the reading part via the light guide member and light incident on thereading part without via the light guide member, at least once in a subscanning direction of the inspection target.
 5. The image inspectionapparatus according to claim 1, further comprising: a light-transmittingmember between the inspection target, and the illumination part and thelight guide member.
 6. The image inspection apparatus according to claim5, wherein the light-transmitting member is arranged to be inclined withrespect to the inspection target.
 7. The image inspection apparatusaccording to claim 5, further comprising: a position maintaining memberthat maintains a position of the inspection target, wherein the positionmaintaining member is installed on the inspection target side of thelight-transmitting member.
 8. The image inspection apparatus accordingto claim 7, wherein the position maintaining member is installed on anupstream side of the inspection target, on the light-transmittingmember.
 9. The image inspection apparatus according to claim 1, whereinan image inspection part including the illumination part, the lightguide member, and the reading part is installed on both sides of theinspection target.
 10. The image inspection apparatus according to claim1, wherein the reading part is a two-dimensional array sensor.
 11. Animage forming apparatus comprising: the image inspection apparatusaccording to claim 1 and an image forming part, wherein the hardwareprocessor adjusts an image forming condition of the image forming partin accordance with a characteristic of the inspection target.